G2 & G3 Controlled Arc Move support

[A Former User]

@T3P3Tony:

I believe CNC GCodes more often contain G2/G3 commands so to widen the applicability of RepRapFirmware this would be good to add. Also there is a bit of chicken and egg. If no firmware supports it then why bother implementing it in a slicer.

Like T3P3Tony pointed out, it would be a first step towards making .stl a thing of the past.
https://www.duet3d.com/forum/thread.php?id=16&p=2

The gcode description:
http://reprap.org/wiki/G-code#G2_.26_G3:_Controlled_Arc_Move

This will help on our way towards .amf support and to get more accurate hole dimensions:
http://forums.reprap.org/read.php?262,407139,737519#msg-737519

[T3P3Tony]

David has released a beta version of this in the 1.17c+1 firmware
https://www.duet3d.com/forum/thread.php?id=797

[jgrouse]

Just checked the state of G2 and G3 in 1.18beta1 and beta3 and it's still not working as expected. If you try this -

G1 X100 Y100 F1000
G2 X150 Y150 I50 J0

You do not end up with a 50mm radius/90 deg CW arc from 100,100 to 150,150 with a centre of rotation at 150,100. Instead you end up with a line to 100,150, a 50mm radius/180 deg CW arc to 200,150 and then a line at the end of the arc to the left back to 150,150 where the arc should of ended.

Correct me if I am misinterpreting the I and J parameters which should be the relative distance from the start point to the centre of the arc - I for the X offset and J for the Y offset? So in my example the centre of rotation is X150 Y100 making I 50 and J 0.

[jgrouse]

Bit more testing and it does appear that in all cases there is an initial Y motion before the arc starts.